Method and composition for delaying the cross-linking of water soluble polymer solutions

ABSTRACT

A stable, non-aqueous liquid suspension of delayed boron cross-linkers comprises an anhydrous boron compound or a sparingly soluble borate suspended in a mixture of mineral spirits (commonly termed as naphtha) and a resin. Anhydrous boron compounds suitable for suspension include, but are not limited to, anhydrous borax, anhydrous boric acid, or a mixture of both the anhydrous borax and anhydrous boric acid. Sparingly soluble borates suitable for suspension include, but are not limited to, alkaline earth metal borates, alkali metal borates, or a mixture thereof. The mixture between the mineral spirits and resin produces a mineral spirits-resin solution. Alternatively, the mineral spirits may be replaced with a suitable oil which forms an oil-resin solution when mixed with the resin. The oil-resin solution suspends the anhydrous boron compound or the sparingly soluble borate to produce a stable, non-aqueous liquid suspension of delayed boron cross-linkers.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of co-pending applicationSer. No. 08/213,868 filed on Mar. 16, 1994.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to compositions for controlling thegelation rates of water soluble polymer solutions used as fracturingfluids in well fracturing operations and, more particularly but not byway of limitation, to suspensions of anhydrous boron compounds in amixture of mineral spirits (commonly termed as naphtha) and a resin or amixture of an oil and a resin. The suspension provides a stable,non-aqueous, pumpable, liquid source of borate ions suitable for use asa gelling agent for water soluble polymer solutions.

2. Description of the Related Art

To perform a hydraulic fracturing operation, a proppant-laden watersoluble polymer hydraulic fracturing fluid such as guar, hydroxypropylguar (HPG), carboxymethyl guar (CMG), or carboxymethyl hydroxypropylguar (CMHPG) may be injected under high pressure into a formationthrough a well bore. Once the natural confining pressures of theformation rock are exceeded, the fracturing fluid initiates a fracturein the formation rock that generally continues to grow during pumping.Hydraulic fracturing of the formation typically requires the fracturingfluid to reach its maximum viscosity as it enters the fracture.Increased viscosity of the fracturing fluid, which improves its abilityto fracture the formation rock, usually occurs through the gelling ofthe water soluble polymer solution utilized as the hydraulic fracturingfluid. Gelation of water soluble polymer solutions may be achieved bythe addition of aluminum, boron, titanium, or zirconium ions, ormixtures thereof to the solution.

However, if the fracturing fluid gels within the well bore, itencounters a high shear due to the limited cross-sectional area withinthe well bore. High shear experienced in the well bore may causeextensive and irreparable degradation in the cross-linked fracturingfluid. Furthermore, high viscosities in the fracturing fluid produceexcessive back or friction pressures within the well bore and formation,thereby limiting the pumping rate and possibly the success of thehydraulic fracturing operation. Various borate ion cross-linking systemshave been developed which delay the gelation of the fracturing fluidduring its pumping through the well bore.

One such borate ion cross-linking system is disclosed in U.S. Pat. No.4,619,776 issued on Oct. 28, 1986, to Mondshine. Mondshine discloses asuspension of alkaline earth metal borates, alkali metal borates, ormixtures thereof. The boron minerals are typically suspended in dieseloil and are sparingly soluble in the water soluble polymer solutions.After the introduction of the Mondshine borate suspension into a watersoluble polymer solution, the suspension slowly thins and dissipates torelease borate ions to gradually cross-link the polymer solution. Thatis, the slow solubility of the suspended, sparingly soluble borateminerals creates a cross-linking system that delays the transformationof polymer solutions into gelled, highly viscous fracturing fluids.

Although the borate ion cross-linking system disclosed by Mondshine willdelay the gelation of water soluble polymer solutions, it suffers fromnumerous disadvantages. First, the suspension of the borate mineral indiesel oil creates a potential environmental hazard. Toxic aromatics andbenzene derivatives contained in the diesel oil might contaminate marineenvironments or ground water sources that maybe proximate to the dieselborate suspensions at well sites. Second, the utilization of borateminerals decreases the effectiveness of the suspension. Impurities inthe boron minerals reduce the quantity of boron in the suspension whichproduces corresponding lower levels of borate ions upon the dispersionof the suspension in a water soluble polymer solution. Third, theimpurities in the borate minerals introduce variability in the delaytime. The exact solubility of the borate minerals are not determinablewith a high degree of accuracy and vary widely depending upon theconditions of use. Fourth, the borate mineral suspensions are usableonly in cases where the bottom hole temperature of the formation ishigher than about 150° F. That limitation occurs due to the very lowsolubility of the borate minerals and the excessive thermal delay intheir cross-linking action. Finally, and perhaps most importantly, theborate mineral suspensions disclosed in Mondshine are highly unstable insuspension. That is, the suspension of the borate minerals in diesel oilmay not be stored for any length of time and is highly susceptible tosettling. It has been observed that the borate minerals, even after evena short length of time in storage settle to the bottom of the containerin which they are stored and agglomerate into a solid. When the borateminerals cake to form a solid, the suspension becomes unusable. Evenconsiderable shaking will not cause the borate minerals to becomere-suspended. This tendency to settle may result in considerable loss ofusable material.

An alternative borate ion cross-linking system is disclosed in U.S. Pat.Nos. 5,082,579; 5,145,590; and 5,160,643 issued on Jan. 21, 1992; Sep.8,1992; and Nov. 3, 1992, respectively, to Dawson. These patents disclosea borate ion based aqueous complexor solution that delays the gelationof water soluble polymer solutions. The aqueous complexor solutionconsists of a cross-linking additive that provides borate ions and adelay additive in solution that serves to chemically bond with theborate ions to reduce the availability of boron to the hydrated polymersolution.

Although the Dawson borate ion cross-linking system providesimprovements to some of the deficiencies characteristic of Mondshine'steaching, such as lack of control over the gelation rate, Dawson'ssystem still suffers from a number of disadvantages. The amount ofavailable borate ions in solution may be insufficient to cross-link allof the polymer in solution due to the presence of the delay additive.The dilution of borate ions caused by the presence of the delay additivecreates a demand for considerably higher quantities of borate ions thanrequired in a stoichiometrically balanced system. The requirement foradditional boron in excess of that necessary for a stoichiometricallybalanced system increases the cost of the Dawson borate ioncross-linking system. A further economic disadvantage of the Dawsonsystem is caused by the undesirable necessity of using large quantitiesof carbonate buffers, such as potassium carbonate, to obtain effectivedelay and temperature stability of the fracturing fluid. Furthermore,due to the presence of the delay additive in solution with the borateions, the cross-linking action of the complexor solution is thermallydelayed. That thermal delay restricts use of the Dawson system toformations having bottom hole temperatures higher than 125° F. Finally,and perhaps most importantly, during storage, the borate ions inDawson's complexor solution precipitate rendering the complexor solutiondeficient in boron.

Accordingly, any borate ion cross-linking system that is stable duringstorage, especially under severe weather conditions, yields 100% of itsavailable boron to soluble borate ions, provides a large operationaltemperature range, and a wide range of cross-link delay times whileretaining precise control of the specific delay is highly desirable.

SUMMARY OF THE INVENTION

In accordance with the present invention, a stable, non-aqueous liquidsuspension of delayed boron cross-linkers comprises an anhydrous boroncompound suspended in a mixture of mineral spirits (commonly termednaphtha) and a resin. Anhydrous boron compounds suitable for suspensioninclude, but are not limited to, anhydrous borax, anhydrous boric acid,or a mixture of both the anhydrous borax and anhydrous boric acid. Themixture between the mineral spirits and the resin produces a mineralspirits-resin solution. Alternatively, the mineral spirits may bereplaced with a suitable oil to form an oil-resin solution utilized tosuspend the anhydrous boron compound.

The suspension of delayed boron cross-linkers may be prepared byslurrying an anhydrous boron compound with mineral spirits or oil,followed by the gradual addition of the resin. After the gradualaddition of the resin, the resulting product is mixed until theanhydrous boron compound is completely and uniformly suspended withinthe mineral spirits-resin solution or the oil-resin solution.

Similarly, the suspension of delayed boron cross-linkers may be preparedby slurring anhydrous boron compound with the resin followed by thegradual addition of the mineral spirits or oil. After the gradualaddition of the mineral spirits or oil, the resulting product is mixeduntil the anhydrous boron compound is completely and uniformly suspendedwithin the mineral spirits-resin solution or oil-resin solution.

Alternatively, mineral spirits or oil and the resin may be mixed to formthe mineral spirits-resin solution or the oil-resin solution followed bythe gradual addition of an anhydrous boron compound. After the additionof the anhydrous boron compound, the resulting product is mixed untilthe anhydrous boron compound is completely and uniformly suspendedwithin the mineral spirits-resin solution or oil-resin solution.

The suspension of delayed boron cross-linkers exhibits many advantagesover currently available delayed borate ion cross-linking systems.First, 100% of the boron present in the suspended anhydrous boroncompound converts to soluble borate ions because the suspended anhydrousboron compounds are completely water soluble. That is, the anhydrousboron compound contains available B₂ O₃ which completely dissolves inthe water soluble polymer solution to release borate ions which thencross-link the water soluble polymer solution. Second, the suspension ofdelayed boron cross-linkers operate to cross-link water soluble polymersolutions in an improved temperature range of from about 80° F. to about325° F. due to the complete availability of the boron in the anhydrousboron compound and the absence of chelates (i.e., complexing agents) asin Dawson or the crystal lattice bonding of boron as in Mondshine.Third, the suspension of delayed boron cross-linkers are stable onaging, even under severe winter conditions, due to their non-aqueouscomposition and relatively high viscosity compared to current boratesuspensions such as Mondshine's.

Finally, the anhydrous nature of the suspended boron compound furnishesa wide range of delay times (from 30 seconds to 10 minutes) while stillproviding a great degree of precision over those delay times. Cross-linktimes are controlled by varying any one of or all of the following:

1) the anhydrous boron compound used (e.g., anhydrous borax, anhydrousboric acid, or a mixture of both the anhydrous borax and anhydrous boricacid),

2) the particle size of the anhydrous boron compound in suspension,

3) the pH of the fracturing fluid prior to the addition of thesuspension,

4) the concentration (i.e., loading) of the suspension in the fracturingfluid,

5) the B₂ O₃ content in the suspension, and

6) the temperature of the fracturing fluid.

Although anhydrous boron compounds produce the most effective suspendeddelayed borate cross-linkers due to their complete solubility in watersoluble polymer solutions, sparingly soluble borates may also beutilized. Sparingly soluble borates suitable for use in the suspensioninclude, but are not limited to, alkaline earth metal borates, alkalimetal borates, and mixtures thereof. Suspensions of the sparinglysoluble borates produced using any one of the above-described methodsexhibit the advantages of the anhydrous boron compound suspensions,except the sparingly soluble borates yield fewer borate ions per unitweight of suspended boron compound due to their sparingly solublenature.

It is, therefore, an object of the present invention to provide asuspension that is stable on aging, even under severe weatherconditions.

It is another object of the present invention to provide a suspensionthat is safer for the environment and costs less than currentsuspensions.

It is a further object of the present invention to provide a suspensionthat includes anhydrous boron compounds that yield 100% of total boronto available soluble borate ions.

It is still another object of the present invention to provide asuspension that may include up to about 50% boron as B₂ O₃.

It is still a further object of the present invention to provide asuspension that operates in a temperature range of from about 80° F. toabout 325° F.

It is even another object of the present invention to provide asuspension that furnishes a wide range of cross-linking delay timeswhile still allowing precise control over those times.

It is an even further object of the present invention to provide asuspension of sparingly soluble borates.

Still other objects, features and advantages of the present inventionwill become evident to those skilled in the art in light of thefollowing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A stable, non-aqueous liquid suspension of delayed boron cross-linkerscomprises an anhydrous boron compound suspended in a mixture of mineralspirits (commonly termed as naphtha) and a resin. Anhydrous boroncompounds suitable for suspension include, but are not limited to,anhydrous borax, anhydrous boric acid, or a mixture of both theanhydrous borax and anhydrous boric acid The mixture between the mineralspirits and resin produces a mineral spirits-resin solution. Theanhydrous borax suitable for suspension in the mineral spirits solubleresin comprises 69.2% boron as B₂ O₃ and 30.2% sodium as Na₂ O. Theanhydrous boric acid suitable for suspension in the mineralspirits-soluble resin comprises 100% boron as B₂ O₃. The chemicalformulas for the anhydrous borax and the anhydrous boric acid areexpressed as Na₂ B₄ O₇ and B₂ O₃, respectively.

The resins suitable for mixture with the mineral spirits to create themineral spirits-resin solution utilized in the suspension include, butare not limited to, styrene/isoprene copolymer, styrene ethylenepropylene block polymer, styrene isobutylene copolymer, styrenebutadiene copolymer, polybutylene, polystyrene, polyethylene-propylenecopolymer, and like compounds. The preferred resins are block copolymerswhich include, but are not limited to, styrene ethylene/propylene blockpolymer, hydrogenated styrene block polymers, and styrene butadienecopolymers. The most preferred block copolymers are hydrogenatedstyrene/isoprene block polymers which are sold under the trademark"BARARESIN VIS" by Baroid Corporation and under the trademark "SHELLVIS40" and SHELLVIS 50"by Shell Chemical Company".

The suspension may be prepared by slurrying an anhydrous boron compoundwith mineral spirits followed by the gradual addition of the resin.After the gradual addition of the resin, the resulting product is mixeduntil the anhydrous boron compound is completely and uniformly suspendedwithin the mineral spirits-resin solution.

Similarly, the suspension may be prepared by slurrying the anhydrousboron compound with the resin followed by the gradual addition of themineral spirits. After the gradual addition of the mineral spirits, theresulting product is mixed until the anhydrous boron compound iscompletely and uniformly suspended within the mineral spirits-resinsolution.

Alternatively, mineral spirits and the resin may be mixed to form themineral spirits-resin solution followed by the gradual addition of theanhydrous boron compound. After the addition of the anhydrous boroncompound, the resulting product is mixed until the anhydrous boroncompound is completely and uniformly suspended within the mineralspirits-resin solution.

Using any one of the above-described methods, the suspension is preparedby supplying the mineral spirits in a range of from about 20% to about40% by weight, the resin in a range of from about 20% to about 60% byweight, and the anhydrous boron compound in a range of up to andincluding 50% by weight.

In an alternative embodiment of the stable, non-aqueous liquidsuspension of delayed boron cross-linkers, the mineral spirits may bereplaced with a suitable oil such as any hydrocarbon oil which includes,but is not limited to, vegetable oils, crude oil, kerosene, pentane,decane, soybean oil, corn oil, and the like. When an oil is substitutedfor the mineral spirits, the oil and resin mix to form an oil-resinsolution which suspends the anhydrous boron compound. Additionally, theabove-described methods remain the same as well as the proportions ofthe oil, resin, and anhydrous boron compound (i.e., from about 20% toabout 40% by weight oil, from about 20% to about 60% by weight resin,and up to and including 50% by weight anhydrous boron compound).

EXAMPLE OF DELAYED BORON CROSS-LINKERS AND CORRESPONDING METHODS OFPREPARATION EXAMPLE I

A suspension may be prepared by mixing mineral spirits in an amount of25% total weight with styrene/isoprene copolymer in an amount of 25%total weight for five minutes utilizing an overhead stirrer. At theexpiration of the five minutes, anhydrous borax, having a particle sizeof smaller than 20 mesh, is gradually added in an amount of 50% totalweight. After the anhydrous borax has been added, the resulting productis mixed for 15 minutes utilizing the overhead stirrer. The suspensionresulting from the above-method contains boron as B₂ O₃ in an amount of33.4% by weight.

EXAMPLE II

A suspension may be prepared by slurrying anhydrous borax in an amountof 33.3% total weight with mineral spirits in an amount of 36.8% totalweight for five minutes utilizing an overhead stirrer. The anhydrousborax in this-example has a particle size of smaller than 60 mesh. Atthe expiration of the five minutes, styrene/isoprene copolymer in anamount of 29.9% total weight is gradually added. After thestyrene/isoprene copolymer has been added, the resulting product mixedfor 15 minutes utilizing an overhead stirrer. The suspension resultingfrom the above method contains boron as B₂ O₃, in an amount of 22.2% byweight.

EXAMPLE III

A suspension may be prepared by mixing mineral spirits in an amount of33.33% total weight with styrene/isoprene copolymer in an amount of33.33% total weight for five minutes utilizing an overhead stirrer. Atthe expiration of the five minutes, anhydrous boric acid having aparticle of size smaller 60 mesh is gradually added in an amount of33.33% total weight. After the anhydrous boric acid has been added, theresulting product is mixed for 15 minutes utilizing an overhead stirrer.The suspension resulting from the above-method contains boron as B₂ O₃in an amount of 33.33% by weight.

The suspensions produced using the mineral spirits or oil, resin, andanhydrous boron compound employing the above-described methods provide astable, pumpable, liquid source of borate ions suitable as cross-linkingagents for water soluble polymer solutions utilized in well-fracturingoperations. To perform a hydraulic fracturing operation utilizing thesuspension, a water soluble polymer solution such as guar, hydroxypropylguar (HPG), carboxymethyl guar (CMG), or carboxymethyl hydroxypropylguar (CMHPG) is prepared using any of several well known methods such asthat disclosed in U.S. Pat. No. 5,160,643. The pH of the water solublepolymer solution is adjusted to between about 8.5 and about 12.5, usingany of several well known methods such a that disclosed in U.S. Pat. No.5,160,643. Once the pH of the solution has been properly adjusted, thesuspended delayed borate cross-linking suspension is combined with thewater soluble polymer solution, and the resulting mixture pumped intothe formation. As is typical in hydraulic fracturing operations,proppants designed to maintain a highly conductive fracture are usuallyincorporated into the fracturing fluid.

Upon contact with the water soluble polymer solution, the cross-linkingsuspension generates borate ions. More particularly, the anhydrousborax, anhydrous boric acid, or the mixture of both, suspended in themineral spirits-soluble resin are released from suspension and dissolveinto the water soluble polymer solution, thereby releasing borate ionsinto the water soluble polymer solution. As the borate ions enter thewater soluble polymer solution, they act as bonding agents (cross-links)between the molecules of the water soluble polymer solution. Thefracturing fluid resulting from the cross-linked water soluble polymersolution is extremely viscous and transports proppants uniformly intothe hydraulically induced fracture in the formation rock. The reactionwhich produces the cross-linked water soluble polymer fracturing fluidmay be illustrated as follows: ##STR1##

The suspension exhibits many advantages over currently available delayedborate ion cross-linking systems. First, 100% of the total boron in thesuspended anhydrous boron compound converts into soluble borate ionsbecause the anhydrous boron compounds are completely water soluble andbecause the pH of the hydrated polymer solution is between about 8.5 andabout 12.5. That is, the anhydrous borax and boric acid each comprisepure B₂ O₃ which completely dissolves in the alkaline water solublepolymer solution to release borate ions which then cross-link the watersoluble polymer solution. Second, the suspensions operate to cross-linkwater soluble polymer solutions in an improved temperature range of fromabout 80° F. to about 325° F. due to the complete availability of boronin the anhydrous boron compound and the absence of chelates (i.e.,complexing agents). Third, the suspensions are stable on aging, evenunder severe weather conditions, due to their non-aqueous compositionand relatively high viscosities.

Finally, the anhydrous nature of the suspended borax, boric acid, ormixture of both, furnishes a wide range of delay times (from 30 secondsto 10 minutes) while still providing a great degree of precision overthose delay times. Cross-link times are controlled by varying any one ofor all of the following:

1) the anhydrous boron compound used,

2) the particle size of the anhydrous boron compound in suspension,

3) the pH of the fracturing fluid prior to the addition of thesuspension,

4) the concentration (i.e., loading) of the suspension in the fracturingfluid,

5) the B₂ O₃ content in the suspension, and

6) the temperature of the fracturing fluid.

Illustratively, When used under similar conditions, the type of boroncompound (i.e., anhydrous borax, anhydrous borax acid, or a mixture ofboth) may be employed effectively to control the exact cross-linkingtime of a water soluble solution. More particularly, suspensions ofanhydrous borax cross-link a water soluble polymer solution more slowlythan suspensions of anhydrous boric acid. Accordingly, suspensions ofmixtures of both anhydrous borax and anhydrous boric acid cross-linkwater soluble polymer solutions over a range of times between theextreme cross-link ranges produced by suspensions solely of eitheranhydrous borax or anhydrous boric acid.

With respect to the particle size of the suspended anhydrous borax,anhydrous boric acid, or mixture of both, as particle size increases,the time required for the suspension of delayed boron cross-linkers tocross-link a water soluble polymer solution increases. Conversely, asthe particle size decreases, the time required for the suspension ofdelayed boron cross-linkers to cross-link a water soluble polymersolution decreases. Particle sizes of the anhydrous borax, anhydrousboric acid, or mixture of both suitable for suspension in the mineralspirits-soluble resin, range from about 20 mesh to about 325 mesh.

The pH of the water soluble polymer solution prior to its cross-linkingby the suspension of delayed boron cross-linkers is utilized to controlcross-link times. The pH of the water soluble polymer solution affectsthe solubility rate of the suspension. Specifically, as the pH of thewater soluble polymer solution increases, the solubility rate increasesif the suspension contains a majority of anhydrous boric acid particles,whereas the solubility rate decreases if the suspension contains amajority of anhydrous borax particles. Conversely, as the pH of thewater soluble polymer solution decreases, the solubility rate decreasesif the suspension contains a majority of anhydrous boric acid particles,whereas the solubility rate increases if the suspension contains amajority of anhydrous borax particles.

Both the concentration (i.e., loading) of the suspension of the delayedboron cross-linkers in the water soluble polymer solution and thecontent of the B₂ O₃ in the suspension of delayed boron cross-linkersboth affect cross-link time of the water soluble polymer solutionsimilarly. That is, as both the concentration of the suspension ofdelayed boron cross-linkers in the water soluble polymer solution andthe content of the B₂ O₃ in the suspension increase, the cross-link timeof the water soluble polymer solution decreases. Conversely, as both theconcentration of the suspension of the delayed boron cross-linkers inthe water soluble polymer solution and the content of the B₂ O₃ in thesuspension decrease, the cross-link time of the water soluble polymersolution increases.

Temperature may be used to alter the cross-link time of a water solublepolymer solution. As the temperature of the water soluble polymersolution increases, its cross-link time decreases. Conversely, as thetemperature of the water soluble polymer solution decreases, itscross-link time increases.

                  TABLE I                                                         ______________________________________                                        Base gel: 40 ppt guar                                                         1 liter tap H.sub.2 O                                                         pH = 12.0                                                                     Loading of boron                                                                          Suspension of  Suspension of                                      suspension in water                                                                       Example I      Example II                                         soluble polymer                                                                           Total Cross-Linking                                                                          Total Cross-Linking                                solution    Time           Time                                               ______________________________________                                        0.5 gpt     >5 min.        >5 min.                                            1.0 gpt     >5 min.        >5 min.                                            1.5 gpt     >5 min.        1 min. 10 sec.                                     2.0 gpt     >5 min.        30 sec.                                            ______________________________________                                    

Table 1 lists the total cross-linking times of a water soluble polymersolution cross-linked under variable loading conditions (0.5-2.0gpt--gallons of suspension/thousand gallons of water soluble polymersolution) utilizing the suspensions described above in Examples I andII. The water soluble polymer used was a 40 ppt (pounds ofpolymer/thousand gallons of water) guar having a pH of 12.0. As listed,the suspensions of delayed boron cross-linkers tested produce variationsin cross-link times of from greater than 5 minutes to highlyreproducible times Of from 1 minute and 10 seconds to 30 secondsdepending upon the loading of the suspension of delayed boroncross-linkers.

Although anhydrous boron compounds produce the most effective suspendeddelayed borate cross-linkers due to their complete solubility in watersoluble polymer solutions, sparingly soluble borates may also besuspended in the mineral spirits-resin solution or the oil-resinsolution. Sparingly soluble borates suitable for use in the suspensioninclude, but are not limited to, alkaline earth metal borates, alkalimetal borates, or mixtures thereof. Suspensions of the sparingly solubleborates exhibit the advantages of the anhydrous boron compoundsuspensions, except the sparingly soluble borates yield fewer borateions per unit weight of suspended boron compounds in water solublepolymer solutions due to their sparingly soluble nature.

Suspensions of the sparingly soluble borates may be prepared using anyone of the above-described methods. Furthermore, the quantities of themineral spirits or oil, resin, and the sparingly soluble borates remainthe same as for the suspensions of anhydrous boron compounds.Specifically, using any one of the above-described methods, thesuspension is prepared by supplying the mineral spirits in a range offrom about 20% to about 40% by weight, the resin in a range of fromabout 20% to about 60% by weight, and the sparingly soluble borates in arange of up to and including 50% by weight.

EXAMPLE SPARINGLY SOLUBLE BORATE SUSPENSIONS EXAMPLE I

A suspension may be prepared by mixing mineral spirits in an amount of33.33% total weight with styrene/isoprene copolymer in an amount of33.33% total weight for five minutes utilizing an overhead stirrer. Atthe expiration of the five minutes, is gradually added in an amount of33.33% total weight. After the ulexite has been added, the resultingproduct is mixed for 15 minutes utilizing an overhead stirrer.

EXAMPLE II

A suspension may be prepared by mixing mineral spirits in an amount of33.33% total weight with styrene/isoprene copolymer in an amount of33.33% total weight for five minutes utilizing an overhead stirrer. Atthe expiration of the five minutes, colemanite is gradually added in anamount of 33.33% total weight. After the colemanite has been added, theresulting product is mixed for 15 minutes utilizing an overhead stirrer.

Although the present invention has been described in terms of theforegoing embodiment, such description has been for exemplary purposesonly and, as will be apparent to those of ordinary skill in the art,many alternatives, equivalents, and variations of varying degree willfall within the scope of the present invention. That scope, accordingly,is not to be limited in any respect by the foregoing description,rather, it is defined only by the claims which follow.

We claim:
 1. A composition for delaying the cross-linking of watersoluble polymer solutions, comprising an anhydrous boron compound or asparingly soluble borate suspended in a solution selected from the groupconsisting of a mineral spirits-resin solution and an oil-resinsolution.
 2. The composition according to claim 1 wherein said anhydrousboron compound is selected from the group consisting of anhydrous borax,anhydrous boric acid, and mixtures thereof.
 3. The composition accordingto claim 1 wherein said sparingly soluble borate is selected from thegroup consisting of alkaline earth metal borates, alkali metal borates,and mixtures thereof.
 4. The composition according to claim 1 whereinsaid mineral spirits-resin solution comprises mineral spirits mixed witha resin.
 5. The composition according to claim 1 wherein said oil-resinsolution comprises an oil mixed with a resin.
 6. The compositionaccording to claim 4 or 5 wherein said resin is selected from the groupconsisting of styrene/isoprene copolymer, styrene ethylene propyleneblock polymer, styrene isobutylene copolymer, styrene butadienecopolymer, polybutylene, polystyrene, polyethylene-propylene copolymer.7. The composition according to claim 4 or 5 wherein said resin is ablock copolymer.
 8. The composition according to claim 7 wherein saidblock copolymer is selected from the group consisting of a styreneethylene/propylene block polymer, a hydrogenated styrene block polymer,and a styrene butadiene copolymer.
 9. The composition according to claim7 wherein said block copolymer is a hydrogenated styrene/isoprene blockpolymer.
 10. The composition according to claim 5 wherein said oil isselected from the group consisting of vegetable oils, crude oil,kerosene, pentane, decane, soybean oil, and corn oil.
 11. A process ofmanufacturing a suspension which delays the cross-linking of watersoluble polymer solutions, comprising the steps of:mixing a resin withminerals spirits to form a mineral spirits-resin solution; adding ananhydrous boron compound or a sparingly soluble borate; mixing theanhydrous boron compound or the sparingly soluble borate and the mineralspirits-resin solution until the anhydrous boron compound or sparinglysoluble borate is suspended within the minerals spirits-resin solution.12. The process according to claim 11 wherein the resin comprises fromabout 20% to about 60% total suspension weight.
 13. The processaccording to claim 11 wherein minerals spirits comprises from about 20%to about 40% total suspension weight.
 14. The process according to claim11 wherein the anhydrous boron compound or the sparingly soluble boratecomprises up to and including 50% total suspension weight.
 15. A processof manufacturing a suspension which delays the cross-linking of watersoluble polymer solutions, comprising the steps of:mixing a resin withan oil to form an oil-resin solution; adding an anhydrous boron compoundor a sparingly soluble borate; mixing the anhydrous boron compound or asparingly soluble borate and the oil-resin solution until the anhydrousboron compound or sparingly soluble borate is suspended within theoil-resin solution.
 16. The process according to claim 15 wherein theresin comprises from about 20% to about 60% total suspension weight. 17.The process according to claim 15 wherein the oil comprises from about20% to about 40% total suspension weight.
 18. The process according toclaim 15 wherein the anhydrous boron compound or sparingly solubleborate comprises up to and including 50% total suspension weight.